Ceramic recuperators for the heating of fluid adapted to form fuel/air mixtures are described, inter alia, in the aforementioned copending application and the literature there cited. Reference may also be had to German patent document (printed application-Auslegeschrift) DT-AS No. 27 07 290.
In general ceramic recuperators are known for the preheating of combustion air for oil burners and like combustion systems, utilizing combustion-gas heat which is indirectly transferred through the body of the ceramic recuperator to the combustion air to be pre-heated before being fed to the burner in the formation of the fuel/air mixture.
The preheating of the combustion air in this manner is of an energy-conserving nature, facilitates the efficient mixing of the fuel with the air and improves the burner output markedly.
During the operation of the oil burner, the preheating of the combustion air in the recuperator is effected by waste gases (combustion gases) drawn from the combustion chamber.
For the cold starting of the oil burner, hot combustion gases are not yet available and hence a preheating of the combustion air therewith is not possible. Until the combustion gases are generated at a sufficient temperature and in a sufficient quantity, the recuperative effect is limited.
In most cases the combustion air must be preheated even for cold starting of an oil heater to render the fuel sufficiently flowable or to induce vaporization of the fuel for proper combustion.